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<div class="iris_headline">IRIS Toolbox Reference Manual</div>




<h2 id="modellang/difflog">difflog</h2>
<div class="headline">First log-difference pseudofunction</div>

<h4 id="syntax">Syntax</h4>
<pre><code>difflog(Expr)
difflog(Expr,K)</code></pre>
<h4 id="description">Description</h4>
<p>If the input argument <code>K</code> is not specified, this pseudofunction expands to</p>
<pre><code>(log(Expr)-log(Expr{-1}))</code></pre>
<p>If the input argument <code>K</code> is specified, it expands to</p>
<pre><code>(log(Expr)-log(Expr{K}))</code></pre>
<p>The two derived expressions, <code>Expr{-1}</code> and <code>Expr{K}</code>, are based on <code>Expr</code>, and have all its time subscripts shifted by --1 or by <code>K</code> periods, respectively.</p>
<h4 id="example">Example</h4>
<p>The following two lines of code</p>
<pre><code>difflog(Z)
difflog(X{1}/Y{-1},-2)</code></pre>
<p>will expand to</p>
<pre><code>(log(Z)-log(Z{-1}))
(log(X{1}/Y{-1})-log(X{-1}/Y{-3}))</code></pre>

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<div class="copyright">IRIS Toolbox. Copyright &copy; 2007-2014 Jaromir Benes.</div>
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